Preparation Of Inorganic Layered Filler/Polymer Thermal Conductive Composites

The wide application of electronic products has brought a lot of convenience to human beings.People are constantly pursuing the high-performance,lightweight and small-sized electronic products,which ensure using special and lightweight materials.As a matrix of thermally conductive composite materials,polymers possess a small density that metal radiators are too heavy to be used.In our study,the high-pressure homogenizer is used to exfoliate the inorganic layered material and mix with the polymer micropowder.The inorganic layered material—graphite and boron nitride?BN?is used as the heat conductive filler.The polymer—nylon 6,polylactic acid and chitosan is used as a substrate to prepare different types of composite materials.Finally,we proposed a facile and effective method for fabricate composites with high through-plane thermal conductivity.Firstly,the polylactic acid micropoder with the particle diameter of 14?m and graphite sheet are uniformly dispersed in water by a solution method.The graphite is exfoliated and refined to fabricate graphite nanosheets by a high-pressure homogenizer,and the exfoliated graphite nanosheets and the polylactic acid micropowder are also subjected to micron mix in the solution.The mixing effect is batter than other mixers or extruders,so that we can not find the re-aggregating graphite nanosheets in the PA/C composites.The thermal conductivity of the composites was 2.35 W/m·K with 40 wt%graphite loading.The cross-sectional scanning electron micrograph of the composites confirmed that the graphite nanosheets in the hot-pressed composites tend to be aligned in the horizontal direction,and the high loading graphite nanosheets can be uniformly dispersed in the composites.Secondly,after exfoliated by the high-pressure homogenizer,the dopamine is polymerized onto the surface of the BN by?-?interaction.The Raman patterns confirm the successful coating of dopamine on BN.The dopamine functionalized BN is modified with a silane coupling agent to graft the amino group onto the surface of the BN.Then,the multi-walled carbon nanotubes are subjected to amidation treatment with aminated BN.The Transmission electron micrograph shows that the boron nitride surface is covered with carbon nanotubes.Raman spectrum and FTIR images confirmed the formation of carboxylic acid on the surface of the carbon nanotubes.The thermal conductivity of the boron nitride-carbon nanotube/nylon 6?BN-CNT/PA?composites were 1.34 W/m·K with 40 wt%loading,which was 3.57 times higher than that of pure nylon 6.Finaly,the homogeneously exfoliated BN is centrifuged and mixed with chitosan under alkaline conditions to form a homogeneous solution,and boron nitride/chitosan microspheres?BN-CS-M?are formed under the emulsifier and crosslinker.When the centrifugation rate is small,a large number of boron nitride nanosheets are embedded on the surface of the microspheres.As the centrifugation rate increases,the Boron nitride nanosheets?BNNSs?on the surface of the microspheres decrease,and the morphology of the microspheres and the morphology of the chitosan microspheres are more similar.When the centrifugal rate of the boron nitride dispersion was 500 rpm,the prepared microspheres had a micropore diameter of1.7 nm and a specific surface area of 269.58 m²·g^-1.